Raney cobalt hydrogenation

Recently another family of dendrimers has become commercially available. These polyamines were developed by Meijer and de Brabander-van den Berg of DSM Research and are based on Vogtle s initial synthesis [7]. In this case the troublesome reduction step was performed using a Raney cobalt hydrogenation catalyst and other process improvements have permitted this synthesis to be continued up to the fifth generation with multikilogram quantities available. 

Cobalt catalysts are generally known to be less active than nickel catalysts for the hydrogenation of aromatic compounds (see, e.g., Table 11.2).4,5 However, properly prepared reduced cobalt or Raney Co have been reported to be more active than the corresponding nickel catalysts in the hydrogenation of benzene13-15 and naphthalene.15... 

Adiponitrile undergoes the typical nitrile reactions, eg, hydrolysis to adipamide and adipic acid and alcoholysis to substituted amides and esters. The most important industrial reaction is the catalytic hydrogenation to hexamethylenediarnine. A variety of catalysts are used for this reduction including cobalt—nickel (46), cobalt manganese (47), cobalt boride (48), copper cobalt (49), and iron oxide (50), and Raney nickel (51). An extensive review on the hydrogenation of nitriles has been recendy pubUshed (10). 

Reduction. Hydrogenation of dimethyl adipate over Raney-promoted copper chromite at 200°C and 10 MPa produces 1,6-hexanediol [629-11-8], an important chemical intermediate (32). Promoted cobalt catalysts (33) and nickel catalysts (34) are examples of other patented processes for this reaction. An eadier process, which is no longer in use, for the manufacture of the 1,6-hexanediamine from adipic acid involved hydrogenation of the acid (as its ester) to the diol, followed by ammonolysis to the diamine (35). 

In a much different approach based on cyanamide, acrylonitrile, and acetonitrile, cyanoacetamidine [56563-07-6] (32) is cyanoethylated and the condensation product [56563-10-1] (33) is dehydrogenated and hydrogenated direcdy to Grewe diamine in the presence of Raney cobalt and ammonia (56). 

This type of catalyst is not limited to nickel other examples are Raney-cobalt, Raney-copper and Raney-ruthenium. When dry, these catalysts are pyrophoric upon contact with air. Usually they are stored under water, which enables their use without risk. The pyrophoric character is due to the fact that the metal is highly dispersed, so in contact with oxygen fast oxidation takes place. Moreover, the metal contains hydrogen atoms and this adds to the pyrophoric nature. Besides the combustion of the metal also ignition of organic vapours present in the atmosphere can occur. Before start of the reaction it is a standard procedure to replace the water by organic solvents but care should be taken to exclude oxygen. Often alcohol is used. The water is decanted and the wet catalyst is washed repeatedly with alcohol. After several washes with absolute alcohol the last traces of water are removed. 

Under relatively mild conditions the Ru/C catalyst poisoned with Sn (lines 1 and 2), the Ir/C catalyst (lines 14 and 15), and the Raney-cobalt catalyst modified with CoCl2 (line 19) seem likely systems to try when initiating a search for an effective method for selectively hydrogenating the C=0 bond in an a, 3-unsaturated aldehyde. 

Isophorone diamine is synthesized traditionally by aminoreduction of iso-phoronenitrile. Raney cobalt was used for this process. More recently, a new two-step process was patented. The first step consists of synthesizing the imine and the second one of hydrogenating the latter. Ra-Ni was used as catalyst at 150°C and 60 bar hydrogen pressure. Under these conditions, the catalyst reduces the nitrile groups and is able to cleave the N-N bonds, too. Ammonia is required to promote primary amine formation during nitrile hydrogenation (Scheme 4.151).554... 

Various other reducing methods are employed for the conversion of (3-nitro alcohols to amino alcohols, namely, electrochemical reduction.107 The selective electrohydrogenation of ni-troaliphatic and nitroaromatic groups in molecules containing other groups that are easy to hydrogenate (triple bond, nitrile, C-I) are carried out in methanol-water solutions at Devarda copper and Raney cobalt electrodes (Eq. 6.55).107... 

Cyclododecene may be prepared from 1,5,9-cyclododecatriene by the catalytic reduction with Raney nickel and hydrogen diluted with nitrogen, with nickel sulfide on alumina, with cobalt, iron, or nickel in the presence of thiophene, with palladium on charcoal, with palladimn chloride in the presence of water, with palladium on barium sulfate, with cobalt acetate in the presence of cobalt carbonyl, and with cobalt carbonyl and tri- -butyl phosphine. It may also be obtained from the triene by reduction with lithium and ethylamine, by disproportionation, - by epoxidation followed by isomerization to a ketone and WoliT-Kishner reduction, and from cyclododecanone by the reaction of its hydrazone with sodium hydride. ... 

Catalytic hydrogenation of thiophene poses a problem since noble metal catalysts are poisoned, and Raney nickel causes desulfurization. Best catalysts proved to be cobalt polysulfide [425], dicobalt octacarbonyl [426], rhenium heptasulfide [5i] and rhenium heptaselenide [54]. The last two require high temperatures (230-260°, 250°) and high pressures (140, 322 atm) and give 70% and 100% of tetrahydrothiophene (thiophane, thiolene), respectively. 

Also, Klabunovskii reported pressure dependences of the OYs in enantio-differentiating hydrogenations of ethyl acetoacetate (EAA) with ruthenium (67), Raney cobalt (65), and RNi catalysts (69) modified with TA, c. Additives. Additives which are added to the reaction system often exert a remarkable effect on the OY of the enantio-differentiating hydrogenation of M A A (23-25). Water is one such additive. For example, in most hydrogenations with amino acid MRNis, the direction of differentiation was reversed by the addition of small amounts of water as shown in Fig. 14 (23, 25). 

Sumimoto introduced a new sebacic acid process including several catalytic hydrogenation reactions.342 The synthesis starts with naphthalene, which is first partially hydrogenated to tetralin over cobalt oxide or molybdenum oxide, then to decalin over ruthenium or iridium on carbon. The selectivity to cw-decalin is better than 90%. In a later phase of the synthesis 5-cyclododecen-l-one is hydrogenated over Raney nickel to obtain a mixture of cyclododecanone and cyclodode-canol in a combined yield of 90%. The selectivity of this step is not crucial since subsequent oxidation of either compound leads to the endproduct sebacic acid. 

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